1. Field of the Invention
The present invention relates generally to low frequency audio systems.
2. Description of the Prior Art
A number of audio systems have been patented, proposed, and sold commercially that use some form of motional feedback. Many of these systems have been created for the purpose of replacing the last bastion of the open loop in high fidelity audio systems with one that is controlled by way of a feedback system. For example, U.S. Pat. No. 5,031,221 to Yokoyama discloses a dynamic loudspeaker driving apparatus that can detect motional voltage with accuracy and then negatively feedback the detected voltage. Additionally, U.S. Pat. Nos. 4,550,430 and 3,798,374 to Meyers, show the use of motional feedback to reduce loudspeaker distortion. Another motional feedback system, described in U.S. Pat. No. 4,180,706 to Bakgaard, provides a transducer producing in the low frequency range a feedback signal proportional to the accelerations of the woofer membrane.
However, no existing system has been universally successful. That is, no system has been successful in the sense of largely replacing conventional directly-driven loudspeakers in their many configurations, including sealed box systems, ported systems, those using passive as well as active radiators, and multiple audio systems.